For example, JP 2011-166727 A (corresponding to US 2011/0169475 A1) discloses a signal output circuit that can reduce generation of radio noise when a switching element such as MOSFET is pulse-width-modulation (PWM) driven.
In the signal output circuit disclosed in JP 2011-166727 A, a capacitor is connected between a gate and a source of the MOSFET, and a gate terminal is provided with relatively large gate capacitance. A charging current for charging the gate capacitance when the MOSFET is changed from an off-state to an on-state, and a discharging current for discharging the gate capacitance when the MOSFET is changed from the on-state to off-state are generated in a current mirror circuit. Variation of the gate voltage of the switching element is alleviated using a time constant between an internal resistance of the current mirror circuit and the gate capacitance. As a result, when the MOSFET is turned on and turned off, a gradient of a waveform of current applied to a load by the MOSFET can be alleviated, and radio noise can be reduced.